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Ryan L McCarthy - Dissertation.pdf (5.4 MB)

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Spatial Pattern, Demography, and Functional Traits of Desert Plants in a Changing Climate

McCarthy, Ryan L.
http://orcid.org/0000-0002-7421-228X
http://rave.ohiolink.edu/etdc/view?acc_num=osu165207799002993

Abstract Details

2022, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
Desert plant communities throughout the arid Southwest are being impacted by a rapidly changing climate. In the Mojave and Sonoran Deserts, severe drought, linked to global climate change, is causing widespread mortality of long-lived species. Biotic interactions, both competitive and facilitative, mediate plant responses to stressful conditions. Consequently, the spatial pattern of plants on the landscape, which determines the intensity of interactions between individuals, is a legacy of past conditions, a moderator of present drought mortality, and a driver of future community change. To better understand how interactions between adjacent individuals affects the rates of growth, survival, and mortality of desert shrubs in a changing climate, in Chapter One I investigated the spatial demography of the numerically dominant species, Ambrosia dumosa (Asteraceae), using a size and neighbor-classified matrix model parameterized with twenty years of data from a permanent one-hectare site in Joshua Tree National Park that spanned periods of historically average climate and extreme drought. I classified 9,215 Ambrosia individuals into six size classes and two neighbor states. Differences in the demography of isolated and neighbored population subsets of this species shifted with drought, illustrating how spatial pattern mediates the impact of climate change. High interannual and intra-annual variability in rainfall challenges desert shrub seedlings with a tradeoff between drought tolerance and competitive ability. I hypothesized that Ambrosia seedlings can acclimate to wetter or drier conditions by modifying their proportion of roots and leaves, based on early-life moisture cues. In Chapter Two I performed a greenhouse experiment to investigate how root/shoot allocation of Ambrosia was affected by variation in the timing of water availability. Seedlings received the same total quantity of water, differing only in the timing of water delivery. Seedlings lacking water for the first four weeks post-germination developed a significantly higher mean root/shoot ratio than the cohort of seedlings receiving water during their first four weeks of growth. These differences persisted even when water availability changed later in development, indicating that seedlings of this species set their root allocation strategy based on experiences of drought early in life. Understanding the processes that drive nonrandom spatial patterns of growth and survival requires a strong link between pattern and process. In Chapter Three, to improve the ecological realism of spatial pattern analysis, I developed a new method of integrating neighboring vegetation density (implemented in R as package vegdensity) as a continuous-area analogue to the commonly used spatial point-pattern method of Ripley’s K function. I applied this method to data on the spatial distribution of two species with the greatest landscape canopy cover, Larrea tridentata (Zygophyllaceae) and Ambrosia dumosa. Despite contrasting patterns of the locations of individuals, where Ambrosia locations cluster while Larrea locations are distributed randomly, both species had a statistically significant deficit of neighboring conspecific vegetation density when compared against a null hypothesis of random plant sizes, given their locations. This result reveals that the sizes of individuals of both species are structured by intraspecific interactions, even when their locations give the illusion of a lack of interactions.
Maria Miriti (Advisor)
Stephen Hovick (Committee Member)
G. Matthew Davies (Committee Member)
Elizabeth Marschall (Committee Member)
172 p.
Biostatistics; Conservation; Demography; Ecology
Climate change; drought; spatial pattern; arid vegetation; Mojave desert; spatial statistics; demography; functional traits; Ambrosia dumosa; Larrea tridentata; Joshua Tree National Park; ecology; phenotypic plasticity; spatial point pattern analysis; spatial statistics

Recommended Citations

Citations

  • McCarthy, R. L. (2022). Spatial Pattern, Demography, and Functional Traits of Desert Plants in a Changing Climate [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu165207799002993

    APA Style (7th edition)

  • McCarthy, Ryan. Spatial Pattern, Demography, and Functional Traits of Desert Plants in a Changing Climate. 2022. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu165207799002993.

    MLA Style (8th edition)

  • McCarthy, Ryan. "Spatial Pattern, Demography, and Functional Traits of Desert Plants in a Changing Climate." Doctoral dissertation, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu165207799002993

    Chicago Manual of Style (17th edition)

osu165207799002993
287
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This open access ETD is published by The Ohio State University and OhioLINK.